This invention relates to mounting an optical element on a rotating shaft, for example, a mirror on the shaft of a galvanometer used for beam scanning.
Even very minor imperfections in the mounted position of the mirror and very minor deviations from flatness of the mirror (e.g., as small as fractions of a micron) can cause unacceptable distortions and inaccuracies in the position of the scanned beam on a surface one meter from the mirror.
Forming the mirror surface integrally with the metal mirror mount, for example by so called replication processes or diamond machining, aids in reducing distortion and mislocation of the mirror which might otherwise be caused by conventional bonding technigues or by differential expansion with change in temperature. Integral mirror/mounts also provide low inertia.
Clamping the mount on the galvanometer shaft can cause mirror distortion or misalignment of the mirror, as a result, for example, of the tolerance between the shaft diameter and the shaft clamp.
Zimmerman, "Strain-free Mounting Techniques for Metal Mirrors", Optical Engineering, March/April, 1981, Vol. 20, No. 2, pp. 187-189, suggests mounting metal mirrors so as to "isolate the mounting strain path from the mirror surface . . . by appropriate geometry."
Lipeler, "Design of Ultralightweight Mirror," Laser Focus/Electro Optics, March, 1984, p. 26, proposes mounting a mirror so as "to spread the load, to avoid transmitting moments, and to make the mirror and its substructure thermally compatible."